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July 10, 2007

Tiny Desert Fish Makes Big Ripple

by Sam Savage

38 fragile pupfish remain as experts scratch heads, mystery's surface

AMARGOSA VALLEY, Nev. -- It's 110 degrees, hardly a heat wave for Death Valley. And in a small, bathtub-warm pool below a steep, rocky incline, small fish appear to be at play, darting and chasing each other through patches of algae.

These are Devils Hole pupfish and, aside from the strangeness of finding fish in the middle of North America's harshest desert, they're about as remarkable to the naked eye as a fat tadpole.

But this particular fish species is revered for helping galvanize public opinion and government efforts to save endangered species. The fish was the focus of a 1976 Supreme Court ruling that became a cornerstone of Western water policy.

Today, the Devils Hole pupfish population has dwindled to 38, confirmed by government divers in their spring count, and the fish has become the object of intense study by federal agencies and private groups trying to stave off its extinction. It also figures in broader research seeking to map a vast aquifer under Nevada and parts of Idaho and Utah and to determine how that groundwater is to be allocated in a fast-growing region that includes Las Vegas.

This pupfish finds itself in a class with some of America's rarest creatures, including the Florida panther and, before its recovery, the whooping crane.

State and federal agencies have spent an estimated $750,000 since 2005 trying to figure out the cause of the fish's decline, Barrett says. Even many critics of the Endangered Species Act of 1973, such as former California congressman Richard Pombo, agree that the pupfish is worth saving.

"You will find people who argue that there's no value in recovering a species like this, but I've never made that argument because, quite frankly, we don't know," says Pombo, whose effort to rewrite the act focused on guarding property rights when they conflict with endangered species' niches. The Devils Hole pupfish was one of the first species put on the endangered list.

Other pupfish are abundant in the West, but the Devils Hole variety is found nowhere else. The 10-foot-by-70-foot thermal pool, hundreds of feet deep, is thought to be the world's smallest known habitat for a vertebrate animal, says Mike Bower of the National Park Service.

In 1952, as a way to protect the fish, President Truman added 40 acres around Devils Hole -- actually a crack in the Earth that opened 60,000 years ago -- to what later became Death Valley National Park.

When the pupfish population collapsed in the 1960s, the Interior Department sued a developer who had pumped so much water from the aquifer that the level at Devils Hole dropped too low for the inch-long fish to thrive. The Supreme Court ruled that the pupfish was entitled to enough water to survive.

Jim Deacon, a retired University of Nevada, Las Vegas, ichthyologist, says publicity about the fish's plight in the 1960s and 1970s, including an Emmy-winning NBC documentary, kindled the fight to preserve vulnerable plants and animals.

"The pupfish became an icon of the movement," he says. "It's had a lot to do with the development of a conservation consciousness."

The species is a tough one for recovery scientists. It has a short life span of about a year. Many adult fish die in winter when food is scarce because no sunlight reaches the hole to fuel algae production.

The fish can't spawn in the hole's deep area because its 93-degree temperature is too warm. Fertilized eggs hatch only in shallow water that cools at night over a small rock "shelf" at one end of the hole.

But the shelf is vulnerable to nature's whims -- water and debris that pour in during flash floods, wind, even earthquakes that slosh water around. The 2004 earthquake and tsunami that devastated parts of Asia created 9-foot swells inside the hole, Bower says.

Gene pool's delicate balance

Scientists have only recently concluded that a gate, fences and platforms installed at the hole during early efforts to protect the fish might unintentionally have messed up its habitat. They now think those structures blunted effects of natural weather cycles that wash away silt and deposit gravel and cobble on the shelf, critical to spawning and food production.

Years ago, Deacon would have to roll back a thick mat of algae to count the fish. Last month, Barrett and Bower were pleased that algae seemed to be growing, though it was sparse by comparison.

Other pupfish can tolerate wide temperature swings and water saltier than the sea, but not those in Devils Hole. That limitation complicates efforts to breed them in captivity, a strategy should some catastrophe wipe out the wild fish.

At Willow Beach National Fish Hatchery on Lake Mojave, a male-female pair of Devils Hole pupfish produced six young this spring. The female died soon after.

"The juveniles are growing very rapidly and they're healthy right now," says Mike Childs, a Fish and Wildlife Service biologist. "We really hope at least one of them, maybe more, will be female."

One theory for the pupfish's demise is that its gene pool narrowed. Another is that a natural change in the hole's algae variety somehow affected food sources. "The only prudent thing to do is hedge our bets and move forward on as many fronts as we can," Bower says.

Last winter, the park service fed the fish artificially for the first time, and they seem healthier and more robust, Barrett says. "But any action has risks, including doing nothing." <>>